Vacuum isolator valve short path


Just wondering, am I supposed to grease these seals?

Do the seals with the rubber gasket need greasing?

I feel like it shouldn’t matter too much? But I don’t know what they’re made of.


Great question. Was thinking this myself and did grease them in my last run because it was leaking in that area.
Although mine has a sleeve that goes over the rings that’s ptfe.

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You always grease any moving parts that touch glass


Thx! Gave em a light lubing

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Wouldn’t lube the bottom o ring as it comes into contact with the product. Lube the green ones up! Also I wrap a few layers of ptfe tape on the glass threads just in case.


Thx :slight_smile:

I usually run ptfe on my seals that touch my flask (can’t afford the fancy apezion grease). Then the rest of the seals I just use the regular Dow Corning grease

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That type of valve is called a tap, check out the part in the description right here.


Ah, free of grease it seems?


If it is leaking and then adding grease fixed it then you may want to get a higher quality valve. You definitely don’t need to grease them normally. We get ours from chemglass.


If you do grease I would stick to the upper ring, the lower green ring greased can more easily expose product to contamination from my experience , especially if you have a super high ultimate vac


I wonder if someone who used this wrote it. It’s not accurate.

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Yes they seal without a gasket, i grease mine to just to be sure

This is the manufacturer, also consider say a solvent distillation head with tap valves or a sep funnel, with a non polar solvent in contact you wouldn’t want any grease near there for sake of dissolving it.

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Again you are mixing principles.

In a sep funnel you use the fluid itself to seal, even the material in flow. You also have a gravity based seal, that does leak just very slowly. And you have a tapered wedge. I would never use grease of those parts.

But for vacuum it has been proven that those ptfe valves after they are used a few times heatand memory affect them. And touching glass bare is worse. You reduce friction and prevent leaks through the glass itself.

Any moving valve that requires to be under vacuum should be greased. Ability to grease allows better stress free turning and less force required to make a seal…

I’ll tell you based on warranty and specifications, not greasing causes more issues than greasing the top part of the glass to allow smooth movement.

This comes from. A performance and warranty notation from my experience. And is a documented trend of success.

Never lubed any of these valves, also never has any sealing problems with the valve. I go by the manufactures instructions, its usually a safe bet.

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Great practice. I’ve had conflicting information with four of my glass and PTFE suppliers. Also statistics lead to warranty factual numbers. The moment we listened to the manufacturer and had customers even somewhat lube the valve we reduced related warranty issues by 90%

I’ve only sold hundreds of valved setups. Don’t listen to me.

sounds like the old sawdust and grease in the differential to hide the gear noises!


How about we ask some facts from a manufacturer

How many valved glassware parts did I return before you told me grease was needed. 75 PC’s maybe over time?
How many have I returned since we started telling customer what you and your valve manufacturer have been saying 0-3pcs?

Actually he will probably remeberberry the PTFE valve fiasco of 2015… But just saying. Tagged him for support on facts.

These valves should definitely have a light coat of grease. I’ve been a manager at said companies in this thread and we always suggest some grease. It’s more to do with ease of plug movement hence not muscling it to tighten or loosen.